Various kinds of leak sensors are widely used for sensing the leakage of water or oil. Representatively, there are a cable type leak sensor, a band type leak sensor, a module type lean sensor or something.
Here, the cable type leak sensor is basically directed to sensing water leakage or oil leakage and to fast informing even a leakage position. The sensing line senses a certain variation (electric potential difference) generating due to a resistance of leaked liquid in relation with the current flowing along a conductive line, which leads to an accurate sensing of water leakage or oil leakage, and even leads to a recognition of leakage position.
The cable type leak sensor costs too much for installing the same, and since the length of a sensor cable is limited to 7 m, 15 m, and 30 m, a customer cannot select a desired length of the product. Since it is disadvantageous that a bracket is additionally needed for installing a sensor, an installation work is hard, and the installation of the bracket requires additional cost. A lot of time is unnecessarily needed for overcoming leakage after the leakage is sensed, and a connection to external device needs a hard work.
In the band type leak sensor, when water contacts with an electric cable while current is flowing, a resistance value changes. So, a water leakage can be sensed depending on a varying resistance value.
The resistance value settable by a leak sensor is 0 Ω˜50Ω, and the output ranges from 30V DC in maximum to 100 mA, and the length of an electric line is 50 m in maximum, and the length of a band sensor is 10 m in maximum.
The band type leak sensor is able to sense the leakage of water or oil with respect to a relatively wider area at a lower cost, and the installation is easier, but a lot of errors occur with respect to a high humidity or an external impact, and it is not easy to sense a correct leak position. Related works for installation are not uniform, a lot of hard work is needed for installing the same. In addition, it is disadvantageous that a lot of investments are needed for the construction of a network or a PC use. Since the length of a cable for sensing a leakage of water or oil is limited to 1 m, 2 m, 5 m, 10 m and 20 m, a selectable range by customers is very limited. The price is relatively high for its performance, and a bracket for fixing the sensor on a bottom where the sensor is to be installed is additionally needed, which leads to a hard installation work and an additional cost. When connecting to an external device, no connection device is provided except the relay contact point method.
In the module type leak sensor, a photo sensor (light receiving part and light emitting part) is disposed in a plastic casing. In a state that liquid is not detected, a beam from the light emitting part is received, but when the beam from the light emitting part senses the liquid, a refraction index changes, so that the beam cannot be inputted into the light receiving part.
Here, the module type leak sensor senses the leakage of water or oil. The input voltage of the above device is 12V DC, and the response time is 50 msm and the available temperature is −10° C.˜60° C. The sensor casing is preferably made of polypropylene.
Here, the module type leak sensor is able to sense a possible leakage portion at a lower cost, and the installation does not cost too much, and an audio alarm and a light alarm can be generated irrespective of surrounding peripherals. No errors due to moisture occur. However, the module type leak sensor is disadvantageously able to sense a very limited specific portion as compared to the cable type leak sensor, and a connection to peripherals needs a very hard work. Since an additional sensor fixing method is needed, a lot of time is needed when installing the product. Since it is designed to sense a very limited specific portion, when the position of leakage changes, it is impossible to detect the changed leaking portion.